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Critical improvements for Map and Set polyfills. #21492
Critical improvements for Map and Set polyfills. #21492
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Importing from an untyped module makes it
any
and is not safe! Did you mean to add// @flow
to the top of_wrapObjectFreezeAndFriends
? (untyped-import
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Importing from an untyped module makes it
any
and is not safe! Did you mean to add// @flow
to the top of_wrapObjectFreezeAndFriends
? (untyped-import
)There was a problem hiding this comment.
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lol
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... with the potential of leaking memory, unreported, if the error happens in the
.delete()
portion of things.Hypothetically; if something wants to call freeze or seal on an object, how likely is it that it actually wouldn't want the
__MAP_POLYFILL_INTERNAL_HASH__
expando applied to the object itself, in the first place? Wouldn't we be better and safer off letting it use the (new-in-this-PR) fallback method instead?There was a problem hiding this comment.
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No, because the fallback method has linear lookup time, compared to the tagging approach, which has constant lookup time. That's a nice advantage of this polyfill over other (better tested, more widely used) polyfills that settle for linear time in order to avoid tagging objects. If we don't care about the performance benefit of tagging, then we should really replace this whole polyfill with one that wasn't invented here.
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I'm confident that
.delete(obj)
will always succeed if.set(obj, obj)
succeeds in puttingobj
into the map. If that invariant does not hold, there's a bug, and we will fix it. And if.set(obj, obj)
fails to putobj
into the map, then there won't be any memory leak, whether or not.delete(obj)
is called/succeeds.